Influence of dwarfing interstock on the tolerance and nutrient utilization efficiency of apple trees under drought stress

Rootstocks play an essential role in supplying water and mineral nutrients to the scion and are used widely to enhance plant resistance to abiotic stresses. We conducted a pot experiment to investigate how the interstock affects the drought tolerance and nutrient uptake and utilization of whole apple trees under drought stress. One-year-old apple trees of the cultivar 'Tianhong 2' on 'Malus. hupenensis Rehd.' rootstock were cultivated with either SH40, Jizhen 1, or Jizhen 2 as an interstock bridge. The Plant height, stem diameter, total dry weight, chlorophyll content, and endogenous hormone content, as well as ionome concentrations, uptake, shift, and partitioning, changed markedly under drought stress. Principal component analysis (PCA) in combination with membership function analysis of growth indices showed that trees with Jizhen 1 as the interstock had higher drought resistance than trees with Jizhen 2 or SH40 as the interstock. Under drought stress, trees with Jizhen 1 as the interstock showed the minimum reduction in macro- and micro-element uptake, and trees with Jizhen 2 as the interstock showed the maximum. PCA and membership function analysis of ionome indices showed that trees with Jizhen 1 as the interstock had higher nutrient uptake and utilization than trees with the other interstocks. These observations highlight the importance of the use of interstock that are adapted to drought stress conditions to ensure optimal nutrient uptake.